1. Field of the Invention
This invention relates to the field of optical scanning and particularly to bar code laser scanners. More particularly it relates to an apparatus and method for sealing the optical surfaces of bar code laser scanners from spilled liquids and other contaminants to which such scanners may be exposed in normal use in a point of sale environment such as a supermarket.
2. Description of Related Art
Supermarket scanners, referred to herein as bar code laser scanners, typically consist of a lower chassis which houses the optical scan line generating elements, a lower sealed window through which the scan lines may pass which is sealed to the chassis, and an upper window which is removable and field replaceable, for example, upon being scratched or broken. In order for the scanner to operate in an optimal fashion, both windows must be optically transparent and free of scratches, smears, discolorations and other contaminants which would prevent the scanner light beam from passing as relatively unimpeded through the windows as possible. This invention relates to a method and apparatus for sealing the space or gap between the lower window and the upper window from contaminants. This space, or gap, as referred to herein, also includes the lower surface of the upper window and the upper surface of the lower window. The distance between the glass windows has high variability and commercial glass varies in thickness and flatness. This presents a requirement for a device capable of sealing the variable distance between the windows and capable of excluding liquids and dust from the gap. Prior art windows not employing a seal have not been able to adequately keep contaminants away from the gap. If contaminants reach the lower window, the lower window must then be cleaned which is frequently difficult, time consuming, and reduces machine availability.